370 The Loess of North America. [May; 



States seems to have been first surmised by Sir Charles Lyell, 

 whose observations, however, were confined to the lower Missis- 

 sippi, and notably to this deposit in the State of that name. He 

 had traveled extensively in Europe, and in the progress of his 

 journeyings had taken occasion to study somewhat carefully the 

 Rhenish loess. In the first edition of his " Elements of Geology," 

 published in 1838, he mentions at some length the loess deposits 

 of the Rhine, and states that it is mineralogically and chemi- 

 cally similar to the famous deposits in the delta of the Nile. He 

 also offers a few considerations touching its origin, to which it is 

 • not here necessary to make reference. Later, in 1846, while 

 Lyell was in this country, Professor Wailes, of the Mississippi 

 Geological Survey, drew his especial attention to the deposit as 

 laid down in certain ravines in Adams county, in that State. In 

 the subsequently published account of his travels, Mr. Lyell 

 remarks that " the resemblance between this loam and the fluvia- 

 tile silt of the valley of the Rhine, generally called loess, is most 

 perfect." 1 Following him, most writers on the loess of the Mis- 

 sissippi valley consider it the counterpart of the Rhenish forma- 

 tion. About this period a large portion of the great hydrographic 

 basin of the Mississippi was being for the first time geologi- 

 cally explored under the general and various State governments, so 

 that discoveries of this deposit over large areas appearing to border 

 upon the principal streams only, were both numerous and important. 

 In Iowa, the first study of the loess was made by Dr. D. D. Owen, 

 and reported upon to the General Government in his " Geological 

 Survey of Wisconsin, Iowa, and Minnesota," published in 1852. 

 He crossed the state from Des Moines, then-a mere military post, 

 to its western limit. Commenting on the rock structure as he 

 advanced, he says :'- " On approaching the Missouri, the hills 

 bordering the extensive bottoms, known as Council Bluffs, attract 

 particular attention, not only from their contour, but from their 

 geological formation. Where vegetation has been removed from 

 their slopes, they are seen to be composed chiefly of a fine ash- 

 colored, silicious marl, or loam, effervescing with acids. In fav- 

 orable situations many species of terrestrial and fluviatile shells 

 were discovered, of the same species as are found in similar 



